Asarco is appealing to federal regulators in its dispute with Union Pacific over lead pollution along railroad lines because it wants to make sure the $1.8 billion it has paid for cleanups is effective.

The Tucson, Arizona, based lead and copper mining company said Monday it filed a petition with the Surface Transportation Board seeking to reevaluate a 2001 decision allowing Union Pacific to abandon certain rail lines in southeast Missouri.

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Asarco lawyer Gregory Evans says the railroad used rock from lead mines in ballast for its rail lines and some ore fell out of trains.